1. Field of the Invention
This invention relates to an ultrasonic obstacle detector mounted on a bumper or the like of a vehicle such as an automotive vehicle, as well as to a method of assembling the same.
2. Description of the Prior Art
FIG. 16 is a side view showing a conventional ultrasonic obstacle detector. FIG. 17 is a front view of FIG. 16. FIG. 18 is a sectional view taken along the line Axe2x80x94A in FIG. 17. FIG. 19 is a rear end view of FIG. 16. FIG. 20 is an exploded side view of FIG. 16 and FIG. 21 is a plan view of FIG. 20 with the case cover opened.
In these figures, reference numeral 1 denotes a sensor case. A case cover 2 for this sensor case 1 is connected along one edge of an open end of the sensor case 1. Engaging claws 3 are integrally formed on an outer wall of the sensor case 1 along the opposite edge of the open end of the sensor case 1. Engaging holes 4 are provided on a free end of the case cover 2 so as to engage with the engaging claws 3. An ultrasonic sensor 5 is partly fit in its periphery into a front end (right in FIG. 18) of the sensor case 2 through a sensor holder 6. This ultrasonic sensor 5 is held between the case cover 2 and the sensor case 1 by pinching them when the case cover 2 is closed.
In FIGS. 18 and 21, a circuit board 7 is contained inside the sensor case 1 with being electrically connected to the ultrasonic sensor 5. A connector lead wire 8 connected to the circuit board 7 is led outside the sensor case 1. As shown in FIG. 16, at a lead-out end of this connector lead wire 8, a connector 9 for external connection is connected. Reference numeral 10 denotes a cap fit in and engaged with a front end of the sensor case 1 with the case cover 2 closed. This cap 10 is to hold the ultrasonic sensor 5 by covering the periphery of the front end of the sensor holder 6, and has integrally formed an outward flange 10a on its front end.
Reference numeral 11 denotes a plate spring which is assembled into the sensor case 1. This plate spring 11 is made up of: a bottom plate 11b having mounting holes 11a (see FIG. 19) which are press-fit into protrusions 1a provided on a rear end surface of the sensor case 1; and arm pieces 11c (four in the figures) which extend from this bottom plate 11b to the vicinity of the outward flange 10a of the cap 10 along the outer wall of the sensor case 1 and the case cover 2. On a front end of the arm pieces 11c articulated portions 11d are provided, which pinches a hole edge portion of a sensor-mounting hole (not shown) formed in a bumper of a vehicle, between the outward flange 10a and the articulated portions 11d. An intermediate portion of each of the arm pieces 11c is engaged with the outer wall portions of the sensor case 1 and the case cover 2, respectively. The portions to be engaged are denoted by reference numerals 11e. 
A description will now be given of the assembly of this detector.
First, the case cover 2 is opened to fit the sensor holder 6, fit-in by the ultrasonic sensor 5, into the front end of the sensor case 1. The circuit board 7 which is electrically connected to the ultrasonic sensor 5 by a connector lead wire 8 is mounted inside the sensor case 1 in the direction perpendicular to the axial direction of the ultrasonic sensor 5. The case cover 2 is then closed with the connector lead wire 8 connected to the circuit board 7 which us led outside, and the engaging holes 4 formed in the case cover 2 are engaged with the engaging claws 3 on the sensor case 1. The ultrasonic sensor 5 is thus pinched by the sensor case 1 and the case cover 2 through the sensor holder 6.
Then, the cap 10 is press-fit into the front end of the sensor case 1 inclusive of the case cover 2 through the peripheral portion of the sensor holder 6. The ultrasonic sensor 5 is thus held by the cap 10. Thereafter, the protrusions 1a on the rear end of the sensor case 1 are press-fit into the mounting holes 11a of the bottom plate 11b. Also, the intermediate portion 11e of each of the arm pieces 11c of the plate springs 11 is engaged with the outer walls of the sensor case 1 and the case cover 2, respectively.
After the ultrasonic obstacle detector has been assembled as described above, a molding resin is filled from a molding opening 2a (see FIG. 21) formed in the case cover 2. The ultrasonic obstacle detector is ultimately completed. When this detector is to be mounted on a bumper of a vehicle, the sensor case 1 inclusive of the case cover 2 is inserted into a sensor-mounting hole formed in the bumper of the vehicle from the rear end of the detector, together with the connector lead wire 8. At the time of inserting the detector, the articulated portions 11d of the arm pieces 11c are elastically deformed inwardly at the hole edge portion of the sensor-mounting hole. When the outward flange 10a of the cap 10 comes into contact with a front surface of the bumper and the articulated portions 11d passed through the sensor-mounting hole, the articulated portions 11d are elastically restored to their original state. As a result, the hole edge portion of the sensor-mounting hole formed in the bumper is pinched between the articulated portions 11d and the outward flange 10a. The ultrasonic obstacle detector can ultimately be mounted on the bumper of the vehicle.
However, there have been a drawback that the number of working steps increases undesirably, and the assembly of the ultrasonic sensor 5 and the cap 10 is troublesome, resulting in a poor working efficiency since the conventional ultrasonic obstacle detector has been constructed as described above. Namely, in order for the ultrasonic sensor 5 to be assembled into the sensor case 1, after the sensor holder 6 into which the ultrasonic sensor 5 is fit into the inside of the front end of the sensor case 1 with the case cover 2 opened, and the engaging claws 3 of the sensor case 1 must be engaged with the engaging holes 4 in the case cover 2 with the case cover 2 closed. In addition, the cap 10 which is used only for the purpose of bringing itself into contact with the front surface of the bumper should be press-fit into the outer walls of the sensor case 1 and the case cover 2, respectively, while sliding along the peripheral edge portion of the sensor holder 6 from the front side thereof.
Furthermore, there has been a drawback that the assembly of the plate spring 11 is time-consuming, resulting in a poor work efficiency since the plate spring 11 has only the ability for mounting the ultrasonic obstacle detector on the bumper of the vehicle. In addition, in assembling the plate spring 11 into the sensor case 1, the mounting holes 11a in the base plate 11b must be press-fit through the protrusion 1a on the rear end of the sensor case 1 along the axial direction. The intermediate engaging portion 11e of each of the arm pieces 11c must further be engaged with the outer walls of the sensor case 1 and the case cover 2, respectively. Still furthermore, the sensor holder 6, the circuit board 7, the cap 10 and the plate spring 11 are assembled one another from the different directions relative to the sensor case 1. In this point, too, much manpower is required for assembling these parts together, resulting in a poor work efficiency.
This invention has been made to solve the above drawbacks, and an object thereof is to provide an ultrasonic obstacle detector which provides an easy integral assembly of a sensor case and a cap by means of a single plate spring, and which exhibits the ability for mounting and fixing the detector to the bumper or the like of a vehicle.
Another object of the invention is to provide an ultrasonic obstacle detector which simplifies the shape of the plate spring, and which easily assembles the plate spring onto the sensor case and the cap.
Still another object of the invention is to provide an ultrasonic obstacle detector which stably and firmly assembles the plate spring relative to the sensor case and the cap.
Still another object of the invention is to provide an ultrasonic obstacle detector which enables easy and sure positioning into the fitting position of the sensor case.
Still another object of the invention is to provide an ultrasonic obstacle detector which enables easy filling of the molding resin into the space formed between the sensor case and the cap.
Still another object of the invention is to provide an ultrasonic obstacle detector which eliminates a connector for external connection with a connector lead wire as a separate part to improve the workability and to reduce the cost.
Still another object of the invention is to provide an ultrasonic obstacle detector which is mountable even on a vehicle with a sensor-mounting portion like a bumper or the like having only a limited depth.
Yet still another object of the invention is to provide an ultrasonic obstacle detector which offers secure water proofness of the connector-inserting portion without requiring a separate part such as a sealing rubber or the like, and which reduces the cost of the materials.
Yet still another object of the invention is to provide an ultrasonic obstacle detector which maintains the strength at the connector-inserting portion.
Yet still another object of the invention is to provide an ultrasonic obstacle detector which is less subject to the influence of heat generated in soldering the connector terminals to the circuit board, and which prevents heat generated in a soldering from being transmitted.
Yet still another object of the invention is to provide an ultrasonic obstacle detector which is less subject to the influence of heat generated in soldering the connector terminals to the circuit board.
Yet still another object of the invention in to provide a method of assembling an ultrasonic obstacle detector which assembles the parts of the detector in one direction to improve the workability.
In order to achieve the above objects, an ultrasonic obstacle detector according to the invention comprises: a sensor case having in a front portion thereof an integrally formed sensor-mounting hollow portion with an outwardly faced flange, an ultrasonic sensor being fit into the sensor mounting hollow; a circuit board contained inside the sensor case and electrically connected to the ultrasonic sensor; a cap fit into an opening of the sensor case; and a plate spring fit onto an outside of the sensor case for engaging with the cap to integrally hold together both the sensor case and the cap, the plate spring having an integrally formed elastic engaging member for pinching a peripheral wall of a sensor-mounting hole between the flange and the elastic engaging member.
The plate spring according to the invention comprises: a substantially U-shaped spring body portion having on each lateral side thereof a leg piece portion which is fit onto an outside of the sensor case; an engaging means hole formed inside of the leg piece portion; an arm-shaped elastic engaging member extending forward from the leg piece portion and elastically deformable in the relative direction each other; and an articulated portion formed in an articulated manner on each front end of the arm-shaped portion so as to pinch the peripheral wall of the sensor-mounting hole of the vehicle between the flange and the articulated portion; the cap having on each outer side wall thereof an engaging claw for engaging into the engaging hole.
The plate spring according to the invention further comprises an intermediate piece portion which extends forward from the spring body portion between both the leg piece portions, and which has an engaging hole formed therein, and the sensor case desirably has an integrally formed engaging protrusion on an outer wall portion thereof for fitting into the engaging hole in the sensor case.
A rugged engaging portion is formed on an open end of the sensor case and a coupling surface of the cap.
A molding resin is filled into an inside space formed between the sensor case and the cap.
An opening is formed in the cap for filling a molding resin therethrough.
A connector formed internally for external connection.
Preferably, the connector is integrally formed with the cap so as to extend relative to the cap in a direction substantially perpendicular to the axial direction of an ultrasonic sensor.
The connector for external connection is arranged such that a connector terminal extends outward beyond the cap.
The connector terminal is plugged into a terminal plug hole formed in the cap such that the connector terminal and the terminal plug hole form a wedge-engagement with each other.
A recessed groove surrounding the terminal plug hole is formed on an inner wall.
A heat shutoff hole is formed near the bottom portion of the connector terminal which is inserted into the circuit board.
A method of assembling an ultrasonic obstacle detector according to the invention comprises: a first step of plugging a connector terminal into a terminal plug hole formed in a cap to be fit into a sensor case; a second step of, after having plugged the terminal, plugging a circuit board through the terminal, soldering, and fitting the sensor case into the cap in a plugging direction of the terminal while containing the circuit board inside the sensor case; and a third step of, after the fitting at the second step, fitting a plate spring onto the sensor case in the plugging direction of the terminal into the cap to engage the plate spring with the cap.